Regarding the state of art relevant to the invention, reference shall be made to the Finnish Pat. No. 55113 wherein bioelectrical functions are observed by measurement of the reactance between an electrode attached to the patient and an electrically conductive antenna outside the patient. The object of the present invention is to develop further the invention disclosed in said reference so that its range of application may be enlarged and the use of electrodes affixed to the patient may be avoided.
It is known in prior art to record the body movements caused by the heartbeat, the so-called cardiac recoil movements, by means of ballistography. In such recording, the patient is supine on a bed which has been tuned to be supported by various kinds of spring systems, wherein the cardiac recoil movement in various planes may be observed and monitored. The method is expensive and requires a well-balanced apparatus and a vibration-free room. Therefore the application of this method in clinical use has remained insignificant. In prior art are known various patient pulse monitoring systems for instance, in which special electrodes have to be connected to the patient and such electrodes, when they become detached, produce as a rule a false alarm. Moreover, during waking time the wearing of these electrodes induces psychological stress. On the other hand the harmful false alarms have on the staff's side been experienced as unsatisfactory, even to such degree that it is preferred to leave the automatic alarms switched off because the false alarms disturb the nursing staff as well as the patients in the ward. Furthermore, the electrodes affixed to the patient restrict the patient's mobility.